[TriEmbed] Coffee roaster sanity check

[Craig Cook]

>Oh wow, that totally slipped past me when I looked at it last.  That 
won't work because the Arduino's power supply is isolated (and that's a 
very good thing).  "GND" in your circuit is an isolated GND; there's no 
path through the MOSFET back to the neutral AC line.  The motor just 
won't run at all.

Ah, I guess that's why the instructables version did not do this, it's why they used a dedicated DC supply for the fan.

Getting the fan to work with AC may be a version 2 improvement. It's not as easy as I thought.

>"Bresenham algorithm"

I'll skip this as well.

>Of course, since you're using an Arduino, you could also do some datalogging,

Yes. That's what I'm working on now. Getting a ESP8266-01 working. I want to connect the system to my home wifi and send data to my desktop to create trend graphs. I want to see current temperature of the thermistor, roast start and end time, each time the SSR starts and stops, etc. I may add a DHT temperature sensor as well to see the current outside air temp to see how it affects roasting time.

After about a year of using of the roaster the beans get over roasted (shortly after that the unit fails and the heater coil breaks). I suspect it is due to the fan motor getting worn out and not cooling the chamber. If I can graph the data for each roast I should see a trend over a few months. I suspect the roasting time will start getting longer when the fan gets worn out.

Using the SSR should extend the unit's life.

If I get all of this working after the next unit failure I may be able to predict when I need to order a spare popcorn maker.

>I might have been too terse in describing what I meant.  The 10k pulling
the SSR input to GND should stay, and a 250-ohm resistor should gobetween the SSR input and the Arduino pin

Ah, I think I have it correct now. Updated the pdf and kicad files.

Thanks

Craig